This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. Introduction: Single-cell recordings in nonhuman primates has demonstrated that midbrain firing to reward cues and reward outcomes is influenced by local reward context: the uncertainty of a given expected reward and the possible reward amounts for a given cue. In a first study, we manipulated the certainty and expected value of anticipated monetary incentives while scanning human participants with FMRI, and found that both uncertainty and reward magnitude increased anticipatory activation in the nucleus accumbens (NAcc), raising the question of how reward context might influence these activations. Specific Aims: In this study, we manipulated reward context within participants, with the aim of determining whether NAcc activation in anticipation of a single incentive could be influenced by which other incentives were available. Methods and Materials: We had participants play two variants of the monetary incentive delay (MID) task (Knutson et al., 2001) in the same scanner session. In one task, participants anticipated both certain and uncertain monetary incentives;in a second task in the same scanning session, participants only anticipated uncertain monetary incentives of the same amounts and probabilities.